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- Research underway on cover crop effects on soil health
These are the decayed remains of a tillage radish and the hole in the soil where it was growing. Photo by Bruce Schultz
An LSU AgCenter research project is underway studying the use of cover crops for the potential to help farmers increase yields, improve soil health, boost soil moisture and decrease fertilizer amounts.
Lisa Fultz, LSU AgCenter soil microbiologist, said the use of some cover crops is believed to sequester soil nitrogen, then make it available when a crop is planted in the spring. “So the farmer wouldn’t have to put out as much nitrogen,” she said.
The study, at the Dean Lee Research and Extension Center near Alexandria and the H. Rouse Caffey Rice Research Station near Crowley, is testing crimson clover, tillage radishes and cereal rye planted on test plots after soybeans are harvested. Before planting soybeans the following year, the cover crops were sprayed with herbicide. No tillage was used.
Many of the radishes were unable to penetrate the hardpan clay soil at Dean Lee, and the roots started growing above the soil line. But weeks after being sprayed with herbicide, the radishes had died, leaving perforations in the soil that allowed moisture to enter the deeper profile of the soil, and the radishes continued to decompose.
“You can see the holes they’ve left,” Fultz said.
Fultz took soil samples after soybeans were planted to check nutrient levels.
The study also includes the economics of cover crops. “If it costs the farmer more than they could hope to make, it’s going to be hard to convince them to plant a cover crop,” she said.
Her preliminary data show a yield decrease is common during the first few years when cover crops are used. Reasons are unknown for the decrease, she said, but yields improve after three to five years.
Fultz said the LSU AgCenter has applied for a grant from the Natural Resources Conservation Service to see if cover crops will serve as hosts for insect pests, and whether cover crops will increase or decrease weed pressure. The project also would include whether cover crops decrease erosion. Corn, cotton, sugarcane and soybeans would be included in the study.
Another study at the Macon Ridge Research Station near Winnsboro is using cover crops in field corn production. Cover crop treatments being used in the study include four legumes and a combination of cereal rye and tillage radishes.
Fultz said the Macon Ridge project showed a 15 percent increase in soil organic matter after the first year that the cover crops were used.
The Macon Ridge study has shown that, so far, the type of cover crop makes no difference. “No cover crop did better than another. Just having something on the soil surface is beneficial.” Bruce Schultz
Lisa Fultz, LSU AgCenter soil microbiologist, takes a soil sample in a cover crop study at the Dean Lee Research and Extension Center near Alexandria. Photo by Bruce Schultz